Suppose some one
should discover
a new mechanical principle -- something as fundamental as James Watt’s
discovery of the expansive power of steam -- by the use of which it
became
possible to build a motor that would give ten horse power for every
pound
of the engine's weight, a motor so simple that the veriest novice in
mechanics
could construct it and so elemental that it could not possibly get out
of repair. Then suppose that this motor could be run forward or
backward
at will, that it could be used as either an engine or a pump, that it
cost
almost nothing to build as compared with any other known form of
engine,
that it utilized a larger percentage of the available power than any
existing
machine, and, finally, that it would operate with gas, steam,
compressed
air or water, any one of them, as its driving power.

It does not take
a mechanical
expert to imagine the limitless possibilities of such an engine. It
takes
very little effort to conjure up a picture of a new world of industry
and
transportation made possible by the invention of such a device.
"Revolutionary"
seems a mild term to apply to it. That, however, is the word the
inventor
uses in describing it -- Nikola Tesla, the scientist whose electrical
discoveries
underlie all modern electrical power development, whose experiments and
deductions made the wireless telegraph possible, and who now, in the
mechanical
field, has achieved a triumph even more far reaching than anything he
accomplished
in electricity.

There is
something of the
romantic in this discovery of the famous explorer of the hidden realms
of knowledge. The pursuit of an ideal is always romantic, and it was in
the pursuit of an ideal which he has been seeking twenty years that Dr.
Tesla made his great discovery. That ideal is the power to fly -- to
fly
with certainty and absolute safety -- not merely to go up in an
aeroplane
and take chances on weather conditions, "holes in the air", tornadoes,
lightning and the thousand other perils the aviator of today faces, but
to fly with the speed and certainty of a cannon ball, with power to
overcome
any of nature's aerial forces, to start when one pleases, go whither
one
pleases and alight where one pleases. That has been the aim of Dr.
Tesla's
life for nearly a quarter of a century. He believes that with the
discovery
of the principle of his new motor he has solved this problem and that
incidentally
he has laid the foundations for the most startling new achievements in
other mechanical lines.

There was a time
when men
of science were skeptical -- a time when they ridiculed the
announcement
of revolutionary discoveries. Those were the days when Nikola Tesla,
the
young scientist from the Balkans, was laughed at when he urged his
theories
on the engineering world. Times have changed since then, and the
"practical"
engineer is not so incredulous about "scientific" discoveries. The
change
came about when young Tesla showed the way by which the power of
Niagara
Falls could be utilized. The right to divert a portion of the waters of
Niagara had been granted; then arose the question of how best to
utilize
the tremendous power thus made available -- how to transmit it to the
points
where it could be commercially utilized. An international commission
sat
in London and listened to theories and practical plans for months.

Up to that time
the only
means of utilizing electric power was the direct current motor, and
direct
current dynamos big enough to be of practical utility for such a
gigantic
power development were not feasible.

Then came the
announcement
of young Tesla's discovery of the principle of the alternating current
motor. Practical tests showed that it could be built -- that it would
work.

That discovery,
at that opportune
time, decided the commission. Electricity was determined upon as the
means
for the transmission of Niagara's power to industry and commerce. Today
a million horse power is developed on the brink of the great cataract,
turning the wheels of Buffalo, Rochester, Syracuse and the intervening
cities and villages operating close at hand the great new
electro-chemical
industries that the existence of this immense source of power has made
possible, while all around the world a thousand waterfalls are working
in the service of mankind, sending the power of their "white coal" into
remote and almost inaccessible corners of the globe, all because of
Nikola
Tesla's first great epoch making discovery.

Today the
engineering world
listens respectfully when Dr. Tesla speaks. The first announcement of
the
discovery of his new mechanical principle was made in a technical
periodical
in mid-September, 1911. Immediately it became the principal topic of
discussions
wherever engineers met.

"It is the
greatest invention
in a century", wrote one of the foremost American engineers, a man
whose
name stands close to the top of the list of those who have achieved
scientific
fame and greatness.

"No invention of
such importance
in the automobile trade has yet been made", declared the editor of one
of the leading engineering publications. Experts in other engineering
lines
pointed out other applications of the new principle and letters asking
for further information poured in on Dr. Tesla from the four quarters
of
the globe.

"Oh, I've had too
much publicity",
he said, when I telephoned to him to ask for an interview in order to
explain
his new discovery to the non-technical public. It took a good deal of
persuasion
before he reluctantly fixed an hour when he would see me, and a good
bit
more after that before he talked at all freely. When he did speak,
however,
he opened up vistas of possible applications of the new engine that
staggered
the imagination of the interviewer.

Looking out over
the city
from the windows of his office, on the twentieth floor of the
Metropolitan
Tower, his face lit up as he told of his life dream and its approaching
realization, and the listener's fancy could almost see the air full of
strange flying craft, while huge steamships propelled at unheard of
speeds
ploughed the waters of the North River, automobiles climbed the very
face
of the Palisades, locomotives of incredible power whisked wheeled
palaces
many miles a minute and all the discomforts of summer heat vanished as
marvelous refrigerating plants reduced the temperature of the whole
city
to a comfortable maximum -- for these were only a few of the
suggestions
of the limitless possibilities of the latest Tesla discovery.

"Just what is
your new invention?",
I asked.

"I have
accomplished what
mechanical engineers have been dreaming about ever since the invention
of steam power", replied Dr. Tesla. "That is the perfect rotary engine.
It happens that I have also produced an engine which will give at least
twenty-five times as much power to a pound of weight as the lightest
weight
engine of any kind that has yet been produced.

"In doing this I
have made
use of two properties which have always been known to be possessed by
all
fluids, but which have not heretofore been utilized. These properties
are
adhesion and viscosity.

"Put a drop of
water on a
metal plate. The drop will roll off, but a certain amount of the water
will remain on the plate until it evaporates or is removed by some
absorptive
means. The metal does not absorb any of the water, but the water
adheres
to it.

"The drop of
water may change
its shape, but until its particles are separated by some external power
it remains intact. This tendency of all fluids to resist molecular
separation
is viscosity. It is especially noticeable in the heavier oils.

"It is these
properties of
adhesion and viscosity that cause the 'skin friction' that impedes a
ship
in its progress through the water or an aeroplane in going through the
air. All fluids have these qualities -- and you must keep in mind that
air is a fluid, all gases are fluids, steam is fluid. Every known means
of transmitting or developing mechanical power is through a fluid
medium.

"Now, suppose we
make this
metal plate that I have spoken of circular in shape and mount it at its
centre on a shaft so that it can be revolved. Apply power to rotate the
shaft and what happens? Why, whatever fluid the disk happens to be
revolving
in is agitated and dragged along in the direction of rotation, because
the fluid tends to adhere to the disk and the viscosity causes the
motion
given to the adhering particles of the fluid to be transmitted to the
whole
mass. Here, I can show you better than tell you."

Dr. Tesla led the
way into
an adjoining room. On a desk was a small electric motor and mounted on
the shaft were half a dozen flat disks, separated by perhaps a
sixteenth
of an inch from one another, each disk being less than that in
thickness.
He turned a switch and the motor began to buzz. A wave of cool air was
immediately felt.

"There we have a
disk, or
rather a series of disks, revolving in a fluid -- the air", said the
inventor.
"You need no proof to tell you that the air is being agitated and
propelled
violently. If you will hold your hand over the centre of these disks --
you see the centres have been cut away -- you will feel the suction as
air is drawn in to be expelled from the peripheries of the disks.

"Now, suppose
these revolving
disks were enclosed in an air tight case, so constructed that the air
could
enter only at one point and be expelled only at another -- what would
we
have?

"You'd have an
air pump",
I suggested.

"Exactly -- an
air pump or
blower", said Dr. Tesla.

"There is one now
in operation
delivering ten thousand cubic feet of air a minute. Now, come over
here."

He stepped across
the hall
and into another room, where three or four draughtsmen were at work and
various mechanical and electrical contrivances were scattered about. At
one side of the room was what appeared to be a zinc or aluminum tank,
divided
into two sections, one above the other, while a pipe that ran along the
wall above the upper division of the tank was connected with a little
aluminum
case about the size and shape of a small alarm clock. A tiny electric
motor
was attached to a shaft that protruded from one side of the aluminum
case.
The lower division of the tank was filled with water.

"Inside of this
aluminum
case are several disks mounted on a shaft and immersed in a fluid,
water",
said Dr. Tesla. "From this lower tank the water has free access to the
case enclosing the disks. This pipe leads from the periphery of the
case.
I turn the current on, the motor turns the disks and as I open this
valve
in the pipe the water flows."

He turned the
valve and the
water certainly did flow. Instantly a stream that would have filled a
barrel
in a very few minutes began to run out of the pipe into the upper part
of the tank and thence into the lower tank.

"This is only a
toy", said
Dr. Tesla. "There are only half a dozen disks -- 'runners', I call them
-- each less than three inches in diameter, inside of that case. They
are
just like the disks you saw on the first motor -- no vanes, blades or
attachments
of any kind. Just perfectly smooth, flat disks revolving in their own
planes
and pumping water because of the viscosity and adhesion of the fluid.
One
such pump now in operation, with eight disks, eighteen inches in
diameter,
pumps four thousand gallons a minute to a height of 360 feet."

We went back into
the big,
well lighted office. I was beginning to grasp the new Tesla principle.

"Suppose now we
reversed
the operation", continued the inventor. "You have seen the disks acting
as a pump. Suppose we had water, or air under pressure, or steam under
pressure, or gas under pressure, and let it run into the case in which
the disks are contained -- what would happen?"

"The disks would
revolve
and any machinery attached to the shaft would be operated -- you would
convert the pump into an engine", I suggested.

"That is exactly
what would
happen -- what does happen", replied Dr. Tesla. "It is an engine that
does
all that engineers have ever dreamed of an engine doing, and more. Down
at the Waterside power station of the New York Edison Company, through
their courtesy, I have had a number of such engines in operation. In
one
of them the disks are only nine inches in diameter and the whole
working
part is two inches thick. With steam as the propulsive fluid it
develops
110-horse power, and could do twice as much."

"You have got
what Professor
Langley was trying to evolve for his flying machine -- an engine that
will
give a horse power for a pound of weight", I suggested.

Ten Horse
Power to the
Pound. ~

"I have got more
than that",
replied Dr. Tesla. "I have an engine that will give ten horse power to
the pound of weight. That is twenty-five times as powerful as the
lightest
weight engine in use today. The lightest gas engine used on aeroplanes
weighs two and one-half pounds to the horse power. With two and
one-half
pounds of weight I can develop twenty-five horse power."

"That means the
solution
of the problem of flying", I suggested.

"Yes, and many
more", was
the reply. "The applications of this principle, both for imparting
power
to fluids, as in pumps, and for deriving power from fluids, as in
turbine,
are boundless. It costs almost nothing to make, there is nothing about
it to get out of order, it is reversible -- simply have two ports for
the
gas or steam, to enter by, one on each side, and let it into one side
or
other. There are no blades or vanes to get out of order -- the steam
turbine
is a delicate thing."

I remembered the
bushels
of broken blades that were gathered out of the turbine casings of the
first
turbine equipped steamship to cross the ocean, and realized the
importance
of this phase of the new engine.

"Then, too", Dr.
Tesla went
on, "there are no delicate adjustments to be made. The distance between
the disks is not a matter of microscopic accuracy and there is no
necessity
for minute clearances between the disks and the case. All one needs is
some disks mounted on a shaft, spaced a little distance apart and cased
so that a fluid can enter at one point and go out at another. If the
fluid
enters at the centre and goes out at the periphery it is a pump. If it
enters at the periphery and goes out at the center it is a motor.

"Coupling these
engines in
series, one can do away with gearing in machinery. Factories can be
equipped
without shafting. The motor is especially adapted to automobiles, for
it
will run on gas explosions as well as on steam. The gas or steam can be
let into a dozen ports all around the rim of the case if desired. It is
possible to run it as a gas engine with a continuous flow of gas,
gasoline
and air being mixed and the continuous combustion causing expansion and
pressure to operate the motor. The expansive power of steam, as well as
its propulsive power, can be utilized as in a turbine or a
reciprocating
engine. By permitting the propelling fluid to move along the lines of
least
resistance a considerably larger proportion of the available power is
utilized.

"As an air
compressor it
is highly efficient. There is a large engine of this type now in
practical
operation as an air compressor and giving remarkable service.
Refrigeration
on a scale hitherto never attempted will be practical, through the use
of this engine in compressing air, and the manufacture of liquid air
commercially
is now entirely feasible.

"With a thousand
horse power
engine, weighing only one hundred pounds, imagine the possibilities in
automobiles, locomotives and steamships. In the space now occupied by
the
engines of the Lusitania twenty-five times her 80,000 horse power could
be developed, were it possible to provide boiler capacity sufficient to
furnish the necessary steam."

"And it makes the
aeroplane
practical", I suggested.

"Not the
aeroplane, the flying
machine", responded Dr. Tesla. "Now you have struck the point in which
I am most deeply interested -- the object toward which I have been
devoting
my energies for more than twenty years -- the dream of my life. It was
in seeking the means of making the perfect flying machine that I
developed
this engine.

"Twenty years ago
I believed
that I would be the first man to fly; that I was on the track of
accomplishing
what no one else was anywhere near reaching. I was working entirely in
electricity then and did not realize that the gasoline engine was
approaching
a perfection that was going to make the aeroplane feasible. There is
nothing
new about the aeroplane but its engine, you know.

"What I was
working on twenty
years ago was the wireless transmission of electric power. My idea was
a flying machine propelled by an electric motor, with power supplied
from
stations on the earth. I have not accomplished this as yet, but am
confident
that I will in time.

"When I found
that I had
been anticipated as to the flying machine, by men working in a
different
field, I began to study the problem from other angles, to regard it as
a mechanical rather than an electrical problem. I felt certain there
must
be some means of obtaining power that was better than any now in use.
And
by vigorous use of my gray matter for a number of years, I grasped the
possibilities of the principle of the viscosity and adhesion of fluids
and conceived the mechanism of my engine. Now that I have it, my next
step
will be the perfect flying machine."

"An aeroplane
driven by your
engine?", I asked.

"Not at all",
said Dr. Tesla.
"The aeroplane is fatally defective. It is merely a toy -- a sporting
play-thing.
It can never become commercially practical. It has fatal defects. One
is
the fact that when it encounters a downward current of air it is
helpless.
The 'hole in the air' of which aviators speak is simply a downward
current,
and unless the aeroplane is high enough above the earth to move
laterally
but can do nothing but fall.

"There is no way
of detecting
these downward currents, no way of avoiding them, and therefore the
aeroplane
must always be subject to chance and its operator to the risk of fatal
accident. Sportsmen will always take these chances, but as a business
proposition
the risk is too great.

"The flying
machine of the
future -- my flying machine -- will be heavier than air, but it will
not
be an aeroplane. It will have no wings. It will be substantial, solid,
stable. You cannot have a stable airplane. The gyroscope can never be
successfully
applied to the airplane, for it would give a stability that would
result
in the machine being torn to pieces by the wind, just as the
unprotected
aeroplane on the ground is torn to pieces by a high wind.

"My flying
machine will have
neither wings nor propellers. You might see it on the ground and you
would
never guess that it was a flying machine. Yet it will be able to move
at
will through the air in any direction with perfect safety, higher
speeds
than have yet been reached, regardless of weather and oblivious of
'holes
in the air' or downward currents. It will ascend in such currents if
desired.
It can remain absolutely stationary in the air, even in a wind, for
great
length of time. Its lifting power will not depend upon any such
delicate
devices as the bird has to employ, but upon positive mechanical
action."

"You will get
stability through
gyroscopes?", I asked.

"Through
gyroscopic action
of my engine, assisted by some devices I am not yet prepared to talk
about",
he replied.

"Powerful air
currents that
may be deflected at will, if produced by engines and compressors
sufficiently
light and powerful, might lift a heavy body off the ground and propel
it
through the air", I ventured, wondering if I had grasped the inventor's
secret.

Dr. Tesla smiled
an inscrutable
smile.

"All I have to
say on that
point is that my airship will have neither gas bag, wings nor
propellers",
he said. "It is the child of my dreams, the product of years of intense
and painful toil and research. I am not going to talk about it any
further.
But whatever my airship may be, here at least is an engine that will do
things that no other engine ever has done, and that is something
tangible."

Scientific
American (30
September 1911), p. 290 ~

"From the Complex to the Simple"

A marked step was
taken in
the simplification of prime movers when Watt's cumbersome beam engine,
with its ingenious but elaborate parallel motion, gave way to the
present
standard reciprocating type, with only piston rod, crosshead and
connecting
rod interposed between piston and crank. An even greater advance toward
ideal simplicity occurred when, after years of effort by inventors to
produce
a practicle rotary, Parsons brought out his compact, though costly,
turbine,
in which the energy of the steam is developed on a zig-zag path through
multitudinous rows of fixed and moving blades.

And now comes Mr.
Tesla with
a motor which bids fair to carry the steam engine another long step
toward
the ideally simple prime mover -- a motor in which the fixed and
revolving
blades of the turbine give place to a set of steel disks of simple and
cheap construction. If the flow of steam in spiral curves between the
adjoining
faces of flat disks is an efficient method of developing the energy of
the steam, the prime mover would certainly appear to have been at last
reduced to its simplest terms.

The further
development of
the unique turbine which we describe elsewhere will be followed with
close
attention by the technical world. The results attained with this small
high-pressure unit are certainly flattering, and give reason to believe
that the addition of a low pressure turbine and a condenser would make
this type of turbine as highly efficient as it is simple and cheap in
construction
and maintenance.

Scientific
American
(30 September 1911), p. 296 ~

"The Rotory Heat Motor Reduced to its
Simplest
Terms"

It will interest
the readers
of the Scientific American to that Nikola Tesla, whose reputation must,
naturally, stand upon the contribution he made to electrical
engineering
when the art was yet in its comparative infancy, is by training and
choice
a mechanical engineer, with a strong leaning to that branch of it which
is covered by the term "steam engineering". For several years past he
has
devoted much of his attention to improvements in thermo-dynamic
conversion,
and the result of his theories and practical experiments is to be found
in an entirely new form of prime movers shown in operation at the
waterside
station of the New York Edison Company, who kindly placed the
facilities
of their great plant at his disposal for carrying on experimental work.

By the courtesy
of the inventor,
we are enabled to publish the accompanying views, representing the
testing
plant at the Waterside station, which are the first photographs of this
interesting motor that have yet been made public.

The basic
principle which
determined Tesla's investigations was the well-known fact that when a
fluid
(steam, gas or water) is used as a vehicle of energy, the highest
possible
economy can be obtained only when the changes in velocity and direction
of the movement of the fluid are made as gradual and easy as possible.
In the present forms of turbines in which the energy is transmitted by
pressure, reaction or impact, as in the De Laval, Parsons, and Curtiss
types, more or less sudden changes both of speed and direction are
involved,
with consequent shocks, vibration and destructive eddies. Furthermore,
the introduction of pistons, blades, buckets, and intercepting devices
of this general class, into the path of the fluid involves much
delicate
and difficult mechanical construction which adds greatly to the cost
both
of production and maintenance.

The desiderata in
an ideal
turbine group themselves under the heads of the theoretical and the
mechanical.
The theoretically perfect turbine would be one in which the fluid was
so
controlled from the inlet to the exhaust that its energy was delivered
to the driving shaft with the least possible losses due to the
mechanical
means employed. The mechanically perfect turbine would be one which
combined
simplicity and cheapness of construction, durability, ease and rapidity
of repairs, and a small ratio of weight and space occupied to the power
delivered on the shaft. Mr. Tesla maintains that in the turbine which
forms
the subject of this article, he has carried the steam and gas motor a
long
step forward toward the maximum attainable efficiency, both theoretical
and mechanical. That these claims are well founded is shown by the fact
that in the plant at the Edison station, he is securing an output of
200
horse-power from a single-stage steam turbine with atmospheric exhaust,
weighing less than 2 pounds per horse-power, which is contained within
a space measuring 2 feet by 3 feet, by 2 feet in height, and which
accomplishes
these results with a thermal fall of only 130 BTU, that is, about
one-third
of the total drop available. Furthermore, considered from the
mechanical
standpoint, the turbine is astonishingly simple and economical in
construction,
and by the very nature of its construction, should prove to possess
such
a durability and freedom from wear and breakdown as to place it, in
these
respects, far in advance of any type of steam or gas motor of the
present
day.

Briefly stated,
Tesla's steam
motor consists of a set of flat steel disks mounted on a shaft and
rotating
within a casing, the steam entering with high velocity at the periphery
of the disks, flowing between them in free spiral paths, and finally
escaping
through exhaust ports at their center. Instead of developing the energy
of the steam by pressure, reaction, or impact, on a series of blades or
vanes, Tesla depends upon the fluid properties of adhesion and
viscosity
-- the attraction of the steam to the faces of the disks and the
resistance
of its particles to molecular separation combining in transmitting the
velocity energy of the motive fluid to the plates and the shaft.

By reference to
the accompanying
photographs and line drawings, it will be seen that the turbine has a
rotor
A which in the present case consists of 25 flat steel disks, one
thirty-second
of an inch in thickness, of hardened and carefully tempered steel. The
rotor as assembled is 3 1/2 inches wide on the face, by 18 inches in
diameter,
and when the turbine is running at its maximum working velocity, the
material
is never under a tensile stress exceeding 50,000 pounds per square
inch.
The rotor is mounted in a casing D, which is provided with two inlet
nozzles,
B for use in running direct and B' for reversing. Openings C are cut
out
at the central portion of the disks and these communicate directly with
exhaust ports formed in the side of the casing.

In operation, the
steam,
or gas, as the case may be is directed on the periphery of the disks
through
the nozzle B (which may be diverging, straight or converging), where
more
or less of its expansive energy is converted into velocity energy. When
the machine is at rest, the radial and tangential forces due to the
pressure
and velocity of the steam cause it to travel in a rather short curved
path
toward the central exhaust opening, as indicated by the full black line
in the accompanying diagram; but as the disks commence to rotate and
their
speed increases, the steam travels in spiral paths the length of which
increases until, as in the case of the present turbine, the particles
of
the fluid complete a number of turns around the shaft before reaching
the
exhaust, covering in the meantime a lineal path some 12 to 16 feet in
length.
During its progress from inlet to exhaust, the velocity and pressure of
the steam are reduced until it leaves the exhaust at 1 or 2 pounds gage
pressure.

The resistance to
the passage
of the steam or gas between adjoining plates is approximately
proportionate
to the square of the relative speed, which is at a maximum toward the
center
of the disks and is equal to the tangential velocity of the steam.
Hence
the resistance to radial escape is very great, being furthermore
enhanced
by the centrifugal force acting outwardly. One of the most desirable
elements
in a perfected turbine is that of reversibility, and we are all
familiar
with the many and frequently cumbersome means which have been employed
to secure this end. It will be seen that this turbine is admirably
adapted
for reversing, since this effect can be secured by merely closing the
right-hand
valve and opening that on the left.

It is evident
that the principles
of this turbine are equally applicable, by slight modifications of
design,
for its use as a pump, and we present a photograph of a demonstration
model
which is in operation in Mr. Tesla's office. This little pump, driven
by
an electric motor of 1/12 horse-power, delivers 40 gallons per minute
against
a head of 9 feet. The discharge pipe leads up to a horizontal tube
provided
with a wire mesh for screening the water and checking the eddies. The
water
falls through a slot in the bottomof this tube and after passing below
a baffle plate flows in a steady stream about 3/4 inch thick by 18
inches
in width, to a trough from which it returns to the pump. Pumps of this
character show an efficiency favorably comparing with that of
centrifugal
pumps and they have the advantage that great heads are obtainable
economically
in a single stage. The runner is mounted in a two-part volute casing
and
except for the fact that the place of the buckets, vanes, etc., of the
ordinary centrifugal pump is taken by a set of disks, the construction
is generally similar to that of pumps of the standard kind.

In conclusion, it
should
be noted that although the experimental plant at the Waterside station
develops 200 horse-power with 125 pounds at the supply pipe and free
exhaust,
it could show an output of 300 horse-power with the full pressure of
the
Edison supply circuit. Furthermore, Mr. Tesla states that if it were
compounded
and the exhaust were led to a low pressure unit, carrying about three
times
the number of disks contained in the high pressure element, with
connection
to a condenser affording 28-1/2 to 29 inches of vacuum, the results
obtained
in the present high-pressure machine indicate that the compound unit
would
give an output of 600 horse-power, without great increase of
dimensions.
This estimate is conservative.

The testing plant
consists
of two identical turbines connected by a carefully calibrated torsion
spring,
the machine to the left being the driving element, the other the brake.
In the brake element, the steam is delivered to the blades in a
direction
opposite to that of the rotation of the disks. Fastened to the shaft of
the brake turbine is a hollow pulley provided with two diametrically
opposite
narrow slots, and an incandescent lamp placed inside close to the rim.
As the pulley rotates, two flashes of light pass out of the same, and
by
means of reflecting mirrors and lenses, they are carried around the
plant
and fall upon two rotating glass mirrors placed back to back on the
shaft
of the driving turbine so that the center line of the silver coatings
coincides
with the axis of the shaft. The mirrors are so set that when there is
no
torsion on the spring, the light beams produce a luminous spot
stationary
at the zero of the scale. But as soon as load is put on, the beam is
deflected
through an angle which indicates directly the torsion. The scale and
spring
are so proportioned and adjusted that the horse-power can be read
directly
from the deflections noted. The indications of this device are very
accurate
and have shown that when the turbine is running at 9,000 revolutions
under
an inlet pressure of 125 pounds to the square inch, and with free
exhaust,
200 brake horse-power are developed. The consumption under these
conditions
of maximum output is 38 pounds of saturated steam per horse-power per
hour
-- a very high efficiency when we consider that the heat-drop, measured
by thermometers, is only 130 BTU, and that the energy transformation is
effected in one stage. Since about three times this number of heat
units
are available in a modern plant with super-heat and high vacuum, the
above
means a consumption of less than 12 pounds per horse-power hour in such
turbines adapted to take up the full drop. Under certain conditions,
however,
very high thermal efficiencies have been obtained which demonstrate
that
in large machines based on this principle, in which a very small slip
can
be secured, the steam consumption will be much lower and should, Mr.
Tesla
states, approximate the theoretical minimum, thus resulting in nearly
frictionless
turbine transmitting almost the entire expansive energy of the steam to
the shaft.

Popular
Mechanics
Magazine (December 1911)

"The Tesla Turbine"

E. F. Stearns

Engineers and men
of science
throughout the world are awaiting with unusual interest the completion
of tests of a new steam turbine designed by Nikola Tesla, which
preliminary
experiments indicate will give enormous power from a comparatively
small
and extremely lightweight engine. Ten horsepower to a pound of weight
has
already been developed with the engines that have been tested and
enthusiasts
who have witnessed the work of the turbine declare the perfect rotor
has
at last been found. To what extent this is true, time and the
construction
of larger units than have yet been used must prove. At present, while
the
practical experimental stage has not yet been passed, the entire
engineering
world is profoundly interested in the work that has been done, and
awaits
future development with much concern.

Operation of the
Tesla engine
depends upon two well-known properties of fluids: adhesion -- the
tendency,
for example, of a certain amount of water to cling to a smooth metal
surface,
even when the bulk of the water has been shaken off; and viscosity, the
resistance of fluids to molecular separation, the tendency of one drop,
in a mass of fluid, to drag adjoining drops with it, if set in motion.

In its simplest
form, the
new idea takes the shape of the inventor's little "air-diffuser". This
consists of half a dozen very thin steel disks, some 9 or 10 in. in
diameter,
set horizontally, about 1/8 in. apart, on the upright shaft of a small,
horizontal electric motor, the center of each disk being cut away in a
3-in. circle. With current switched into the motor, the disks revolve,
and instantly strong suction can be felt by the hand held several
inches
above the axis, while a powerful current of air is blown from the
spaces
between the disks. The air, in short, is being sucked into the central
opening and hurled out at the periphery. Consider now that disks and
shaft
have been inclosed in an air-tight case, with an inlet at the axis and
an outlet at one point of the periphery; we have an air pump, a Tesla
blower,
one of which, now in operation, is delivering 10,000 cu. ft. of air per
minute.

Suppose again
that water,
instead of air, be the fluid admitted. Entering the cut-away space at
the
centers of the disks, the adhesion of the metal drags it, in a widening
spiral, toward the spinning circumferences, there to hurl it away in a
tangential direction; and since the water must now leave the case by
its
one outlet, we have the Tesla pump, on rather new lines.

Assume that the
pumping process
is to be reversed, that the disks, instead of being turned by an
outside
force, are to produce power themselves, that steam under pressure has
been
substituted for the water. The steam, admitted to the case, strikes the
edges of the disks and takes the path of least resistance between them,
a narrowing spiral toward the outlet through their centers. The disks
themselves
are dragged around, the shaft is turned and power is being generated in
an entirely new fashion.

Working under the
best conditions
-- in the experimental laboratory a single disk of 9 3/4 in. diameter,
with a center outlet of 3 5/8 in., will develop 5 hp. Without nearly
approaching
the limit of strain of the materials, the pressure could be increased
so
that the velocity of rotation would be doubled and the power
quadrupled;
so that with a single steel plate, 1/32 in. in thickness, weighing
about
3/8 lb., and delivering 20 hp, we have a possible 53 hp. to 1 lb. of
actually
working material. Or a more concrete example can be found in a double
Tesla
turbine, built for practical service and nearly completed. In this
there
are two sets of disks, arranged to revolve in opposite directions and
each
set developing 200 hp.

A little model
pump in which
five disks, 3 in. in diameter, contained in the lower front, circular
case,
throw 40 gal. a minute when the little electric motor is started up.
The
water flows out of a slit at the bottom of the upper pipe and flows
back
to the lower tank as seen in the foreground. This model illustrates one
point astonishingly: the power can be shut off when the pump is in full
operation and everything stops instantly without the slightest jar.
With
the power switched on suddenly, the full flow is resumed so quickly
that
the interval between the click of the switch and the full stream of
water
is too small to be determined with an ordinary watch.

Complete
System:

Casing
Removed to Show Disks:

Fountain:

US Patent # 1,061,142

"Fluid Propulsion"

Nikola Tesla

Be it known that
I, Nikola
Tesla, and engineer residing at the Waldorf Astoria, corner Fifth
Avenue
and Thirty Fourth Street, in the Borough of Manhattan, City and State
of
New York, United States of America, having invented certain new and
useful
improvements in fluid propulsion, do hereby declare the following is a
full, clear and exact description of the same.

In the practical
application
of mechanical power based on the use of a fluid as vehicle of energy it
has been demonstrated that, in order to attain the highest economy, the
changes in velocity and direction of movement of the fluid should be as
gradual as possible. In the present forms of such apparatus more or
less
sudden changes, shocks and vibrations are unavoidable. Besides the
employment
of the usual devices for imparting to vanes and blades, necessarily
introduce
numerous defects and limitations and adds to the complication, cost of
production and maintenance of the machine.

The object of my
invention
is to overcome these deficiencies and to effect the transmission and
transformation
of mechanical energy through the agency of fluids in a more perfect
manner,
and by means simpler and more economical than those heretofore
employed.

I accomplish this
by causing
the propelled or propelling fluid to move in natural paths or stream
lines
of least resistance, free from constraint and disturbance such as
occasioned
by vanes or kindred devices, and to change its velocity and direction
of
movement by imperceptible degrees, thus avoiding the losses due to
sudden
variations while the fluid is receiving or imparting energy.

It is well know
that a fluid
possesses among others, two salient properties: adhesion and viscosity.
Owing to these a body propelled through such a medium encounters a
peculiar
impediment known as "lateral" or "skin resistance", which is two-fold:
one arising from the shock of the fluid against the asperities of the
solid
substance, the other from internal forces opposing molecular
separation.
As an inevitable consequence a certain amount of the fluid is dragged
along
by the moving body. Conversely, if the body were placed in a fluid in
motion,
for the same reasons, it is impelled in the direction of the movement.

These effects, in
themselves,
are of daily observation, but I believe that I am the first to apply
them
in a practical and economical matter of fluid propulsion. The nature of
my discovery and the principles of construction of the apparatus, which
I have designed for carrying it out, I shall now proceed to describe by
reference to the accompanying drawings which illustrate an operative
and
efficient embodiment of the same.

Figure 1
is a partial
end view, and

Figure 2 a
vertical
cross section of a pump or compressor, which Figures 3 and 4 represent,
respectively, in corresponding views, a rotary engine or turbine, both
machines being constructed and adapted to be operated in accordance
with
my invention.

In these drawings
the device
illustrated contains a runner composed of a plurality of flat rigid
disks
1 of a suitable diameter, keyed to a shaft 2, and held in a position by
a threaded nut 3, a shoulder 4 and washers 5 of the requisite
thickness.
Each disk has a number of central openings 6, the solid portions
between
which form spokes 7, preferably curved, as shown, for the purpose of
reducing
the loss of energy due to the impact of the fluid. The runner is
mounted
in a two-part volute casing 8 having stuffing boxes 9 and inlets 10
leading
to its central portion. In addition a gradually widening and rounded
outlet
11 is provided formed with a flange, for connection to a pipe as usual.
The casing 8 rests upon a base 12 shown only in part and supporting the
bearings for the shaft 2, which being of ordinary construction, are
omitted
from the drawings.

An understanding
of the principle
embodied in this device will be gained from the following description
of
its mode of operation. Power being applied to the shaft and the runner
set in rotation in the direction of the solid arrow, the fluid by
reason
of its properties of adherence and viscosity, upon entering through the
inlets 10 and coming in contact with the disks 1 is taken hold of by
the
same and subjected to two forces, one acting tangentially in the
direction
of rotation, and the other radiates outward. The combined effect of the
tangential and centrifugal forces is to propel the fluid with
continuously
increasing velocity in a spiral path until it reaches the outlet 11
from
which it is ejected. This spiral movement, free and undisturbed and
essentially
dependent on these properties of the fluid, permitting it to adjust
itself
to natural paths or streamlines and to change its velocity and
direction
by insensible degrees, is characteristic of this method of propulsion
and
advantageous in its application. While traversing the chamber enclosing
the runner, the particles of the fluid may complete one or more turns,
or but part of one turn. In any given case their path can be closely
calculated
and graphically represented, but fairly accurate estimates of turns can
be obtained simply by determining the number of revolutions required to
renew the fluid passing through the chamber and multiplying it by the
ratio
between the mean speed of the fluid and that of the disks. I have found
that the quantity of fluid propelled in this manner is, other
conditions
being equal, approximately proportionate to the active surface of the
runner
and to its effective speed. For this reason, their performance of such
machines augments at an exceedingly high rate with the increase of
their
size and speed of revolution.

The dimensions of
the device
as a whole, and the spacing of the disks in any given machine will be
determined
by the conditions and requirements of special cases. It may be stated
that
the intervening distance should be the greater, the larger the diameter
of the disks, the longer the spiral path of the fluid and the greater
its
viscosity. In general, the spacing should be such that the entire mass
of the fluid, before leaving the runner, is accelerated to a nearly
uniform
velocity, not much below that of the periphery of the disks under
normal
working conditions and almost equal to it when the outlet is closed and
the particles move in concentric circles.

It may also be
pointed out
that such a pump can be made without openings and spokes in the runner,
as by using one or more solid disks, each in its own casing, in which
form
the machine will be eminently adapted for sewage, dredging and the
like,
when the water is charged with foreign bodies and spokes or vanes
especially
objectionable.

Another
application of this
principle which I have discovered to be not only feasible, buy
thoroughly
practicable and efficient, is the utilization of machines such as above
described for the compression or rarefaction of air, or gases in
general.
In such cases it will be found that most of the general considerations
obtaining in the case of liquids, properly interpreted, hold true.
When,
irrespective of the character of the fluid, considerable pressure are
desired,
staging or compounding may be resorted to in the usual way, the
individual
runners being, preferably, mounted on the same shaft. It should be
added
that the same end may be attained with one single runner by suitable
deflection
of the fluid through rotational or stationary passages.

The principles
underlying
the invention are capable of embodiment also in that field of
mechanical
engineering which is concerned in the use of fluids as motive agents,
for
while in some respects the actions in the latter case are directly
opposite
to those met with in the propulsion of fluids, the fundamental laws
applicable
in the two case are the same. In other words, the operation described
above
is reversible, for, if water or air, under pressure, be admitted to the
opening 11 the runner is set in rotation in the direction of the dotted
arrow by reason of the peculiar properties of the fluid, which,
traveling
in a spiral path, and with continuously diminishing velocity, reaches
the
orifices 6 and 10 through which it is discharged.

When apparatus of
the general
character described is employed for the transmission of power, however,
certain departures from similarity between transmitter and receiver may
be necessary for securing the best results. I have, therefore, included
that part of my invention which is directly applicable to the use of
fluids
as motive agents in a separate application filed January 17, 1911,
Serial
No. 603,049. It may be here pointed out, however, as is evident from
the
above considerations, that when transmitting power from one shaft to
another
by such machines, any desired ratio between the speeds of rotation may
be obtained by proper selection of the diameters of the disks, or, by
suitably
staging the transmitter, the receiver, or both. But it may be pointed
out
that in one respect, at least, the two machines are essentially
different

In the pump, the
radial or
static pressure, due to centrifugal force, is added to the tangential
or
dynamic, thus increasing the effective head and assisting in the
expulsion
of the fluid. In the motor, on the contrary, the first named pressure
being
opposed to that of supply reduces the effective head and the velocity
of
radial flow towards the center. Again, in the propelled machine, a
great
torque is always desirable, this calling for an increased number of
disks
and smaller distance of separation, while in the propelling machine,
for
numerous economic reasons, the rotary effect should be the smallest and
the speed the greatest practicable. Many other considerations, the
design
and construction, but the preceding is thought to contain all necessary
information in this regard.

It will be
understood that
the principles of construction and operation above generally set forth,
are capable of embodiment in machines of the most widely different
forms,
and adapted for the greatest variety of purposes. In my present
application,
I have sought to describe and explain only the general and typical
applications
of the principle, which I believe I am the first to realize and turn to
useful account.

US Patent # 1,061,206

(6 May 1913)

"Turbine"

Nikola Tesla

Be it known that
I, Nikola
Tesla, a citizen of the United States, residing at New York, in the
county
and State of New York, have invented certain new and useful
Improvements
in Rotary Engines and Turbines, of which the following is a full,
clear,
and exact description.

In the practical
application
of mechanical power, based on the use of fluid as the vehicle of
energy,
it has been demonstrated that, in order to attain the highest economy,
the changes in the velocity and direction of movement of the fluid
should
be as gradual as possible. In the forms of apparatus heretofore devised
or proposed, more or less sudden changes, shocks, and vibration are
unavoidable.
Besides, the employment of the usual deices for imparting to, or
deriving
energy from a fluid, such as pistons, paddles, vanes, and blades,
necessarily
introduces numerous defects and limitations and adds to the
complication,
cost of production and maintenance of the machines.

The object of my
invention
is to overcome these deficiencies and to effect the transmission and
transformation
of mechanical energy through the agency of fluids in a more perfect
manner
and by means simpler and more economical than those heretofore
employed.
I accomplish this by causing the propelling fluid to move in natural
paths
or stream lines of least resistance, free from constraint and
disturbance
such as occasioned by vanes or kindred devices, and to change its
velocity
and direction of movement by imperceptible degrees, thus avoiding the
losses
due to sudden variation while the fluid is imparting energy.

It is well known
that a fluid
possesses, among others, two salient properties, adhesion and
viscosity.
Owing to these a solid body propelled through such a medium encounters
a peculiar impediment known as "lateral" or skin resistance, which is
twofold,
one arising from the shock of the fluid against the asperities of the
solid
substance, the other from internal forces opposing molecular
separation.
As an inevitable consequence a certain amount of the fluid is dragged
along
by the moving body. Conversely, if the body be placed in a fluid in
motion,
for the same reasons, it is impelled in the direction of movement.
These
effects, in themselves, are of daily observation, but I believe that I
am the first to apply them in a practical and economical manner in the
propulsion of fluids or in their use as motive agents.

In an application
filed by
me October 21st, 1909, Serial Number 523,832 of which this case is a
division,
I have illustrated the principles underlying my discovery as embodied
in
apparatus designed for the propulsion of fluids. The same principles,
however,
are capable of embodiment also in that field of mechanical engineering
which is concerned in the use of fluids as motive agents, for while in
certain respects the operations in the latter case are directly
opposite
to those met with in the propulsion of fluids, and the means employed
may
differ in some features, the fundamental laws applicable in the two
cases
are the same. In other words, the operation is reversible, for if water
or air under pressure be admitted to the opening constituting the
outlet
of a pump or blower as described, the runner is set in rotation by
reason
of the peculiar properties of the fluid which, in its movement through
the device, imparts its energy thereto.

The present
application,
which is a division of that referred to, is specially intended to
describe
and claim my dsicovery above set forth, so far as it bears on the use
of
fluids as motive agents, as distinguished from the applications of the
same to the propulsion or compression of fluids.

In the drawings,
therefore,
I have illustrated only the form of apparatus designed for the
thermo-dynamic
conversion of energy, a field in which the applications of the
principle
have the greatest practical value.

Figure 1
is a partial
end view, and

Figure 2 a
vertical
cross-section of a rotary engine or turbine, constructed and adapted to
be operated in accordance with the principles of my invention.

The apparatus
comprises a
runner composed of a plurality of flat rigid disks 13 of suitable
diameter,
keyed to a shaft 16, and held in position thereon by a threaded nut 11,
a shoulder 12, and intermediate washers 17. The disks have openings 14,
adjacent to the shaft and spokes 15, which may be substantially
straight.
For the sake of clearness, but a few disks, with comparatively wide
intervening
spaces, are illustrated.

The runner is
mounted in
a casing comprising two end castings 19, which contain the bearings for
the shaft 16, indicated but not shown in detail; stuffing boxes 21 and
outlets 20. The end castings are united by a central ring 22, which is
bored out to a circle of slightly larger diameter than that of the
disks,
and has flanged extensions 23, and inlets 24, into which finished ports
or nozzles 25 are inserted. Circular grooves 26 and labyrinth packing
27
are provided on the sides of the runner. Supply pipes 28, with valves
29,
are connected to the flanged extensions of the central ring, one of the
valves being normally closed.

For a more ready
and complete
understanding of the principle of operation it is of advantage to
consider
first the actions that take place when the device is used for the
propulsion
of fluids for which purpose let it be assumed that power is applied to
the shaft and the runner set in rotation say in a clockwise direction.
Neglecting, for the moment, those features of construction that make
for
or against the efficiency of the device as a pump, as distinguished
from
a motor, a fluid, by reason of its properties of adherence and
viscosity,
upon entering through the inlets 20, and coming in contact with the
disks
13, is taken hold of by the latter and subjected to two forces, one
acting
tangentially in the direction of rotation, and the other radially
outward.
The combined effect of these tangential and centrifugal forces is to
propel
the fluid with continuously increasing velocity in a spiral path until
it reaches a suitable peripheral outlet from which it is ejected. This
spiral movement, free and undisturbed and essentially dependant on the
properties of the fluid, permitting it to adjust itself to natural
paths
or stream lines and to change its velocity and direction by insensible
degrees, is a characteristic and essential feature of this principle of
operation.

While traversing
the chamber
inclosing the runner, the particles of the fluid may complete one or
more
turns, or but a part of one turn, the path followed being capable of
close
calculation and graphic representation, but fairly accurate estimates
of
turns can be obtained simply by determining the number of revolutions
required
to renew the fluid passing through the chamber and multiplying it by
the
ratio between the mean speed of the fluid and that of the disks. I have
found that the quantity of fluid propelled in this manner is, other
conditions
being equal, approximately proportionate to the active surface of the
runner
and to its effective speed. For this reason, the performance of such
machines
augments at an exceedingly high rate with the increase of their size
and
speed of revolution.

The dimensions of
the device
as a whole, and the spacing of the disks in any given machine will be
determined
by the conditions and requirements of special cases. It may be stated
that
the intervening distance should be the greater, the larger the diameter
of the disks, the longer the spiral path of the fluid and the greater
its
viscosity. In general, the spacing should be such that the entire mass
of the fluid, before leaving the runner, is accelerated to a nearly
uniform
velocity, not much below that of the periphery of the disks under
normal
working conditions, and almost equal to it when the outlet is closed
and
the particles move in concentric circles.

Considering now
the converse
of the above described operation and assuming that fluid under pressure
be allowed to pass through the valve at the side of the solid arrow,
the
runner will be set in rotation in a clockwise direction, the fluid
traveling
in a spiral path and with continuously diminishing velocity until it
reaches
the orifices 14 and 20, through which it is discharged. If the runner
be
allowed to turn freely, in nearly frictionless bearings, its rim will
attain
a speed closely approximating the maximum of that of the adjacent fluid
and the spiral path of the particles will be comparatively long,
consisting
of many almost circular turns. If load is put on and the runner slowed
down, the motion of the fluid is retarded, the turns are reduced, and
the
path is shortened.

Owing to a number
of causes
affecting the performance, it is difficult to frame a precise rule
which
would be generally applicable, but it may be stated that within certain
limits, and other conditions being the same, the torque is directly
proportionate
to the square of the velocity of the fluid relatively to the runner,
and
to the effective area of the disks, and inversely, to the distance
separating
them. The machine will, generally, perform its maximum work when the
effective
speed of the runner is one-half that of the fluid; but to attain the
highest
economy, the relative speed or slip, for any given performance, should
be as small as possible. This condition may be to any desired degree
approximated
by increasing the active area of and reducing the space between the
disks.

When apparatus of
the kind
described is employed for the transmission of power certain departures
from similarity between transmitter and receiver are necessary for
securing
the best results. It is evident that when transmitting power from one
shaft
to another by such machines, any desired ratio between the speeds of
rotation
may be obtained by a proper selection of the diameters of the disks, or
by suitably staging the transmitter, the receiver, or both. But it may
be pointed out that in one respect, at least, the two machines are
essentially
different. In the pump, the radial or static pressure, due to
centrifugal
force, is added to the tangential or dynamic, thus increasing the
effective
head and assisting in the expulsion of the fluid. In the motor, on the
contrary, the first named pressure, being opposed to that of supply,
reduces
the effective head and the velocity of radial flow toward the center.
Again,
in the propelled machine a great torque is always desirable, this
calling
for an increased number of disks and smaller distance of separation,
while
in the propelling machine, for numerous economic reasons, the rotary
effort
should be the smallest and the speed the greatest practicable. Many
other
considerations, which will naturally suggest themselves, may affect the
design and construction, but the preceding is thought to contain all
necessary
information in this regard.

In order to bring
out a distinctive
feature, assume, in the first place, that the motive medium is admitted
to the disk chamber through a port, that is a channel which it
traverses
with nearly uniform velocity. In this case, the machine will operate as
a rotary engine, the fluid continuously expanding on its tortuous path
to the central outlet. The expansion takes place chiefly along the
spiral
path, for the spread inward is opposed by the centrifugal force due to
the velocity of the whirl and by the great resistance to radial
exhaust.
It is to be observed that the resistance to the passage of the fluid
between
the plates is, approximately, proportionate to the square of the
relative
speed, which is maximum in the direction toward the center and equal to
the full tangential velocity of the fluid. The path of least
resistance,
necessarily taken in obedience to a universal law of motion is,
virtually,
also that of least relative velocity. Next, assume that the fluid is
admitted
to the disk chamber not through a port, but a diverging nozzle, a
device
converting wholly or in part, the expansive into velocity-energy. The
machine
will then work rather like a turbine, absorbing the energy of kinetic
momentum
of the particles as they whirl, with continuously decreasing speed, to
the exhaust.

The above
description of
the operation, I may add, is suggested by experience and observation,
and
is advanced merely for the purpose of explanation. The undeniable fact
is that the machine does operate, both expansively and impulsively.
When
the expansion in the nozzles is complete, or nearly so, the fluid
pressure
in the peripheral clearance space is small; as the nozzle is made less
divergent and its section enlarged, the pressure rises, finally
approximating
that of the supply. But the transition from purely impulsive to
expansive
action may not be continuous throughout, on account of critical states
and conditions and comparatively great variations of pressure may be
caused
by small changes of nozzle velocity.

In the preceding
it has been
assumed that the pressure of supply is constant or continuous, but it
will
be understood that the operation will be, essentially the same if the
pressure
be fluctuating or intermittent, as that due to explosions occurring in
more or less rapid succession.

A very desirable
feature,
characteristic of machines constructed and operated in accordance with
this invention, is their capability of reversal of rotation. Fig 1,
while
illustrative of a special case, may be regarded as typical in this
respect.
If the right had valve be shut off and the fluid is rotated in the
direction
of the dotted arrow, the operation, and also the performance remaining
the same as before, the central ring being bored to a circle with this
purpose in view. The same result may be obtained in many other ways by
specially designed valves, ports, or nozzles for reversing the flow, in
the description of which is omitted here in the interest of simplicity
and clearness. For the same reasons but one operative port or nozzle is
illustrated which might be adapted to a volute but does not fit best a
circular bore. It will be understood that a number of suitable inlets
may
be provided around the periphery of the runner to improve the action
and
that the construction of the machine may be modified in many ways.

Still another
valuable and
probably as unique quality of such motors or prime movers may be
described.
By proper construction and observance of working conditions the
centrifugal
pressure, opposing the passage of the fluid, may, as already indicated,
be made nearly equal to the pressure of supply when the machine is
running
idle. If the inlet section be large, small changes in the speed of
revolution
will produce great differences in flow which are further enhanced by
the
concomitant variations in the length of the spiral path. A self
regulating
machine is thus obtained bearing a striking resemblance to a
direct-current
electric motor in this respect that, with great differences of
impressed
pressure in a wide open channel the flow of the fluid through the same
is prevented by virtue of rotation. Since the centrifugal head
increases
as the square of the revolutions, or even more rapidly, and with modern
high grade steel great peripheral velocities are practical, it is
possible
to attain that condition in a single stage machine, more readily if the
runner be of large diameter. Obviously this problem is facilitated by
compounding,
as will be understood by those skilled in the art. Irrespective of its
bearing on economy, this dependency which is, to a degree, common to
motors
of the above description, is of special advantage in the operation of
large
units, as it affords a safeguard against running away and destruction.
Besides these, such a prime mover possesses many other advantages, both
constructive and operative. It is simple, light, and compact, subject
to
but little wear, cheap and exceptionally easy to manufacture as small
clearances
and accurate milling work are not essential to good performance. In
operation
it is reliable, there being no valves, sliding contacts or troublesome
varies. It is almost free of windage, largely independent of nozzle
efficiency
and suitable for high as well as for low fluid velocities and speeds of
revolution.

It will be
understood that
the principles of construction and operation above generally set forth,
are capable of embodiment in machines of the most widely different
forms,
and adapted for the greatest variety of purposes. In my present
specification
I have sought to describe and explain only the general and typical
applications
of the principle which I believe I am the first to realize and turn to
useful account.

US Patent # 1,329,559

(3 February 1920)

"Valvular Conduit"

Nikola Tesla

Be it known that
I, Nikola
Tesla, have invented certain new and useful Improvements in Valvular
Conduits,
of which the following is a full, clear and exact description.

In most of the
machinery
universally employed for the development, transmission and
transformation
of mechanical energy, fluid impulses are made to pass, more or less
freely,
through suitable channels or conduits in one direction while their
return
is effectively checked or entirely prevented. This function is
generally
performed by devices designated as valves, comprising carefully fitted
members the precise relative movements of which are essential to the
efficient
and reliable operation of the apparatus. The necessity of, and absolute
dependence on these, limits the machine in many respects, detracting
from
its practical value and adding greatly to the cost of manufacture and
maintenance.
As a rule the valve is a delicate contrivance, very liable to wear and
get out of order and thereby imperil ponderous, complex and costly
mechanisms
and, moreover, it fails to meet the requirements when the impulses are
extremely sudden or rapid in succession and the fluid is highly heated
or corrosive.

Though these and
other correlated
facts were known to the very earliest pioneers in the science and art
of
mechanics, no remedy has as yet been found or proposed to date so far
as
I am aware and I believe that I am the first to discover or invent any
means, which permit the performance of the above function without the
use
of moving parts, and which permit the performance of the above function
without the use of moving parts, and which it is the object of this
application
to describe.

Briefly
expressed, the advance
I have achieved consists in the employment of a peculiar channel or
conduit
characterized by valvular action.

The invention can
be embodied
in many constructions greatly varied in detail, but for the explanation
of the underlying principle it may be broadly stated that the interior
of the conduit is provided with enlargements, recesses, projections,
baffles
or buckets which, while offering virtually no resistance to the passage
of the fluid in one direction, other than surface friction, constitute
an almost impassable barrier to its flow in the opposite sense by
reason
of the more or less sudden expansions, contractions, deflections,
reversals
of direction, stops and starts and attendant rapidly succeeding
transformations
of the pressure and velocity energies.

For the full and
complete
disclosure of the device and of its mode of action reference is made to
the accompanying drawings in which: --

Figure 1
is a horizontal
projection of such a valvular conduit with the top plate removed.

Figure 2
is a side
view of the same in elevation.

Figure 3
is a diagram
illustrative of the application of the device to a fluid propelling
machine
such as a reciprocating pump or compressor, and

Figure 4
is a plan
showing the manner in which the invention is, or may be used, to
operate
a fluid propelled rotary engine or turbine.

Referring to
Figure 1, 1
is a casing of metal or other suitable material which may be cast,
milled
or pressed from sheet in the desired form. From its side walls extend
alternatively
projections terminating in buckets 2 which, to facilitate manufacture
are
congruent and spaced at equal distances, but need not be. In addition
to
these there are independent partitions 3 which are deemed of advantage
and the purpose of which will be made clear. Nipples 4 and 5, one at
each
end, are provided for pipe connection. The bottom is solid and the
upper
or open side is closed by a fitting plate 6 as shown in Figure 2. When
desired any number of such pieces may be joined in series, thus making
up a valvular conduit of such length as the circumstances may require.

In elucidation of
the mode
of operation let it be assumed that the medium under pressure be
admitted
at 5. Evidently, its approximate path will be as indicated by the
dotted
line 7, which is nearly straight, that is to say, if the channel be of
adequate cross-section, the fluid will encounter a very small
resistance
and pass through freely and undisturbed, at least to a degree. Not so
if
the entrance be at the opposite end 4. In this case the flow will not
be
smooth and continuous, but intermittent, the fluid being quickly
deflected
and reversed in direction, set in swirling motion, brought to rest and
again accelerated, these processes following one another in rapid
succession.
The partitions 3 serve to direct the stream upon the buckets and to
intensify
the actions causing violent surges and eddies which interfere very
materially
with the flow through the conduit. It will be readily observed that the
resistance offered to the passage of the medium will be considerable
even
if it be under constant pressure, but the impediments will be of full
effect
only when it is supplied in pulses and, more especially, when the same
are extremely sudden and of high frequency. In order to bring the fluid
masses to rest and to high velocity in short intervals of time energy
must
be furnished at a rate which is unattainable, the result being that the
impulse cannot penetrate very far before it subsides and gives rise to
movement in the opposite direction. The device not only acts as a
hinderment
to the bodily return of particles but also, in a measure, as a check to
the propagation of a disturbance through the medium. Its efficacy is
chiefly
determined; first, by the magnitude of the ratio of the two resistances
offered to disturbed and undisturbed flow, respectively, in the
directions
from 4 to 5 and from 5 to 4, in each individual element of the conduit;
second, by the number of complete cycles of action taking place in a
given
length of the valvular channel and third, by the character of the
impulses
themselves. A fair idea may be gained from simple theoretical
considerations.

Examining more
closely the
mode of operation it will be seen that, in passing from one to the next
bucket, in the direction of disturbed flow, the fluid undergoes two
complete
reversals or deflections through 180° while it suffers only two
small
deviation from about 10° to 20° when moving in the opposite
sense.
In each case the loss of head will be proportionate to a hydraulic
coefficient
dependent on the angle of deflection from which it follows that, for
the
same velocity, the ratio of the two resistances will be as that of the
two coefficients. The theoretical value of this ratio may be 200 or
more,
but it must be taken as appreciable less although surface friction too
is greater in the direction of disturbed flow. In order to keep it as
large
as possible, sharp bends should be avoided, for these will add to both
resistance and reduce the efficiency. Whenever practicable, the piece
should
be straight; the next best is the circular form.

That the peculiar
function
of such a conduit is enhanced by increasing the number of bucket or
elements
and, consequently, cyclic processes in a given length is an obvious
conclusion,
but there is no direct proportionality, because the successive actions
diminish in intensity. Definite limits, however, are set constructively
and otherwise to the number of elements per unit length of the channel,
and the most economical design can only be evolved through long
experience.

Quite apart from
any mechanical
features of the device the character of the impulses has a decided
influence
on its performance and the best results will be secured, when there are
produced at 4, sudden variations of pressure in relatively long
intervals,
while a constant pressure is maintained at 5. Such is the case in one
of
its most valuable industrial applications which will be specifically
described.

In order to
conduce to a
better understanding, reference may first be made to Figure 3 which
illustrates
another special use and in which 8 is a piston fixed to a shaft 9 and
fitting
freely in a cylinder 10. The latter is closed at both ends by flanged
heads
11 and 12 having sleeves or stuffing boxes 13 and 14 for the shaft.
Connection
between the two compartments, 15 and 16, of the cylinder is established
through a valvular conduit and each of the heads is similarly equipped.
For the sake of simplicity these devices are diagrammatically shown,
the
solid arrows indicating the direction of undisturbed flow. An extension
of the shaft 9 carries a second piston 17 accurately ground to and
sliding
easily in a cylinder 18 closed at the ends by plates and sleeves as
usual.
Both piston and cylinder are provided with inlet and outlet ports
marked,
respectively, 19 and 20. This arrangement is familiar, being
representative
of a prime mover of my invention, termed "mechanical oscillator", with
which it is practicable to vibrate a system of considerable weight many
thousand times per minute.

Suppose now that
such rapid
oscillations are imparted by this or other means to the piston 8.
Bearing
in mind the preceeding, the operation of the apparatus will be
understood
at a glance. While moving in the direction of the solid arrow, from 12
to 11, the piston 8 will compress the air or other medium in the
compartment
16 and expel it from the same, respectively, as closed and open valves.
During the movement of the piston in the opposite direction, from 11
to12,
the medium which has meanwhile filled the chamber 15 will be
transferred
to compartment 16, egress being prevented by the device in head 12 and
that in the piston allowing free passage. These processes will be
repeated
in very quick succession. If the nipples 4 and 5 are put in
communication
with independent reservoirs, the oscillations of the piston 8 will
result
in a compression of air at 4 and rarefaction of the same at 5.
Obviously,
the Valvular channels being turned the other way, as indicated by
dotted
lines in the lower part of the figure, the opposite will take place.
The
devices in the piston have been shown merely by way of suggestion and
can
be dispensed with. Each of the chambers 15 and 16 being connected to
two
conduits as illustrated, the vibrations of a solid piston as 8 will
have
the same effect and the machine will then be a double acting pump or
compressor.
It is likewise unessential that the medium be admitted to the cylinder
through such devices for in certain instances ports, alternately closed
and opened by the piston, may serve the purpose. As a matter of course,
this novel method of propelling fluids can be extended to multistage
working
in which case a number of pistons will be employed, preferably on the
same
shaft and of different diameters in conformity with well established
principles
of mechanical design. In this way any desired ratio of compression or
degree
of rarefaction may be attained.

Figure 4
exemplifies a particularly
valuable application of the invention to which reference has been made
above. The drawing shows in vertical cross section a turbine which may
be of any type but is in this instance one invented and described by me
and supposed to be familiar to engineers. Suffice it to state that the
rotor 21 of the same is composed of flat plates which are set in motion
through the adhesive and viscous action of the working fluid, entering
the system tangentially at the periphery and leaving it at the center.
Such a machine is a thermodynamic transformer of an activity surpassing
by far that of any other prime mover, it being demonstrated in practice
that each single disk of the rotor is capable of performing as much
work
as a whole bucketwheel. Besides, a number of other advantages, equally
important, make it especially adapted for operation as an internal
combustion
motor. This may be done in many ways, but the simplest and most direct
plan of which I am aware is the one illustrated here. Referring again
to
the drawing, the upper part of the turbine casing 22 has bolted to it a
separate casing 23, the central cavity 24 of which forms the combustion
chamber. To prevent injusry through excessive heating a jacket 25 may
be
used, or else water injected, and when these means are objectionable
recourse
may be had to air cooling, this all the more rapidly as very high
temperatures
are practicable. The top of casting 23 is closed by a plate 20 with a
sparking
or hot wire plug 27 and in its sides are screwed two Valvular conduits
communicating with the central chamber 24. One of these is, normally,
open
to the atmosphere while the other connects to a source of fuel supply
as
a gas main 28. The bottom of the combustion chamber terminates in a
suitable
nozzle 29 which consists of separate pieces of heat resisting material.
To regulate the influx of the explosion constituents and secure the
proper
mixture of air and gas conduits are equipped, respectively, with valves
30and 31. The exhaust openings 82 of the rotor should be in
communication
with a ventilator, preferably carried on the same shaft and of any
suitable
construction. Its use, however, while advantageous, is not
indispensable,
the suction produced by the turbine rotor itself being, in some cases
at
least, sufficient to insure proper working. This detail is omitted from
the drawing as unessential to the understanding.

But a few words
will be needed
to make clear the mode of operation. The air valve 30 being open, and
sparking
established across terminals 27, the gas is turned on slowly until the
mixture in the chamber 24 reaches the critical state and is ignited.
Both
the conduits behaving, with respect to efflux, as closed valves, the
products
of combustion rush out through the nozzle 29 acquiring still greater
velocity
by expansion and, imparting their momentum to the rotor 21, start it
from
rest. Upon the subsidence of the explosion the pressure in the chamber
sinks below the atmospheric owing to the pumping action of the rotor or
ventilator and new air and gas is permitted to enter, cleaning the
cavity
and channels and making up a fresh mixture which is detonated as
before,
and so on, the successive impulses of the working fluid producing an
almost
continuous rotary effort. After a short lapse of time the chamber
becomes
heated to such a degree that the ignition device may be shut off
without
disturbing the established regime. This manner of starting the turbine
involves the employment of an unduly large combustion chamber which is
not commendable from the economic point of view, for not only does it
entail
increased heat losses but the explosions cannot be made to follow one
another
with such rapidity as would be desirable to insure the best Valvular
action.
When the chamber is small an auxiliary means for starting, as
compressed
air, may be resorted to and a very quick succession of explosions can
then
be obtained. The frequency will be the greater the stronger the
suction,
and may, under certain circumstances, reach hundreds and even thousands
per second. It scarcely need be stated that instead of one several
explosion
chambers may be used for cooling purposes and also to increase the
number
of active impulses and the output of the machine.

Apparatus as
illustrated
in Figure 4 presents the advantage of extreme simplicity, cheapness and
reliability, there being no compressor, buckets or troublesome valve
mechanism.
It also permits, with the addition of certain well-known accessories,
the
use of any king of fuel and thus meets the pressing necessity of a
self-contained,
powerful, light and compact internal combustion motor for general work.
When the attainment of the highest efficiency is the chief object, as
in
machines of large size, the explosive constituents will be supplied
under
high pressure and provision made of maintaining a vacuum at the
exhaust.
Such arrangements are quite familiar and lend themselves so easily to
this
improvement that an enlargement on this subject is deemed unnecessary.

The foregoing
description
will readily suggest to experts modifications, both as regards
construction
and application of the device and I do not wish to limit myself in
these
respects. The broad underlying idea of the invention is to permit the
free
passage of a fluid through a channel in the direction of the flow and
to
prevent its return through friction and mass resistance, thus enabling
the performance of valve functions without any moving parts and thereby
extending the scope and usefulness of an immense variety of mechanical
appliances.

I do not claim
the methods
of and apparatus for the propulsion of fluids and thermodynamic
transformation
of energy herein disclosed, as these will be made subjects of separate
applications.

I am aware that
asymmetrical
conduits have been constructed and their use proposed in connection
with
engines, but these have no similarity wither in their construction or
manner
of employment with my Valvular conduit. They were incapable of acting
as
valves proper, for the liquid was merely arrested in pockets and
deflected
through 90°, this result having at best only 25% of the efficiency
attained in the construction herein described. In the conduit I have
designed
the fluid, as stated above, is deflected in each cycle through
360°,
and a coefficient approximating 200 can be obtained so that the device
acts a s a slightly leaking valve, and for that reason the term
"Valvular"
has been given to it in contrast to asymmetrical conduits, as
heretofore
proposed, which are not Valvular in action, but merely asymmetrical as
to resistance.

Furthermore, the
conduits
heretofore constructed were intended to be used in connection with
slowly
reciprocating machines, in which case enormous conduit-length would be
necessary, all this rendering them devoid of practical value. By the
use
of an effective Valvular conduit, as herein described, and the
employment
of pulses of very high frequency, I am able to condense my apparatus
and
secure such perfect action as to dispense successfully with valves in
numerous
forms of reciprocating and rotary engines.

The high
efficiency of the
device, irrespective of the character of the pulses, is due to two
causes:
first, rapid reversal of direction of flow and, second, great relative
velocity of the colliding fluid columns, As will be readily seen each
bucket
causes a deviation through an angle of 180°, and another change of
180 degrees occurs in each of the spaces between adjacent buckets. That
is to say, from the time the fluid enters or leaves on of the recesses
to its passage into, or exit from, the one following a complete cycle,
or deflection through 360° is effected. Observe now that the
velocity
is but slightly reduced in the reversal so that the incoming and
deflected
fluid columns meet with a relative speed, twice that of the flow, and
the
energy of their impact is four times greater than with a deflection of
only 90° , as might be obtained with pockets such as have been
employed
in asymmetrical conduits for various purposes. The fact is, however,
that
in these such deflection is not secured, the pockets remaining filled
with
comparatively quiescent fluid and the latter following a winding path
of
least resistance between the obstacles interposed. In such conduits the
action cannot be characterized as Valvular because some of the fluid
can
pass almost unimpeded in a direction opposite to the normal flow. In my
construction, as above indicated, the resistance in the reverse may be
200 times that in the normal direction. Owing to this a comparatively
very
small number of buckets or elements is required for checking the fluid.
To give a concrete idea, suppose that the leak from the first element
is
represented by the fraction 1/X, then after the nth bucket is
traversed,
only a quantity (1/X)n will escape and it is evident that X
need not be a large number to secure a nearly perfect Valvular action.